The summer of 2010 was Charleston's
hottest summer on record. From June-August, the average
temperature was 83.1 degrees, beating the old
record
of 82.6 F set in 1998. Additional records set included the most
consecutive days
above 90
degrees with 74 days (old record was 70 in 1990) and the most nights
with lows above 75 degrees with 53
days
(old record was 45 in 1998.)

Some factors affecting temperatures
in South Carolina are elevation, latitude and
distance inland from the coast. All three of these work together in South Carolina.
Lower temperatures can be expected in the Upper Piedmont and Mountain
Regions, where latitude, elevation and distance inland all have large
values. Higher temperatures are found along the southern coast. Annual
average temperatures are almost 10 degrees lower in the extreme Upper
Piedmont than along the coast between Charleston and Savannah. Except
for small-scale and local irregularities, there is a gradual decrease
in annual average temperature northwestward from 67 at the coast to 58°
F at the edge of the mountains. Within the Mountain Region, variations
are great over short horizontal distances. Thus, variations in
temperature are due almost entirely to elevation differences. Low
temperatures are common in the Mountain Region or extreme Upper
Piedmont during the winter. The lowest on record is -19° F at Caesars
Head January 21, 1985. The air over the coastal water is cooler than
the air over the land in summer and warmer than the air over land in
winter and this has a modifying effect on the temperatures near the
coast. Maximum summer temperatures of 111° F have been reached a few
times at inland locations for the State record. Maximum temperatures in
summer are reduced slightly in areas where afternoon cloudiness and
rain are persistent. Such an area is found along the Outer Coastal
Plain where sea breezes produce clouds and rain during the day, but
dissipate at night. Another effect is the drainage of cold air, mostly
October - April, into some of the river valleys causing low
temperatures to be several degrees colder than they would be otherwise.
One example of this takes place in a rather deep section of the Broad
River valley from Lockhart to just north of Columbia.

The growing season for most crops is
limited by the fall and spring freezes. The freeze-free period, the
time elapsing between the last temperature of 32° F in the spring and
the first in the fall, is quite important to agriculture. The average
length of the freeze-free period varies from about 200 days in the
coldest area to about 280 days along the south coast, but in the area
where most of the major crops are grown it is from 210 to 235 days. The
average date of the last freezing temperature in spring ranges from
early March in the south to the first of April in the north. The fall
dates range from late October in the north to late November in the
south. Freezes have occurred as much as four weeks later than the
average date in spring and three weeks earlier than the average date in
the fall. The minimum temperature is 32° F or less on 50 to 70 days in
the Upper Piedmont and 10 days near the coast. Counties in the Inner
Coastal Plain and the Sand Hills area have maximum temperatures of 90°
F or more on about 80 days. There are 30 such days along the coast and
10 to 30 in the mountains.

South
Carolina precipitation
averages and extremes, Top
10 climate extremes, precipitation data for all U.S.
states
Data source: National Climatic Data Center